A repellent is a substance designed to deter unwanted organisms, such as insects or animals, from approaching or infesting a specific area. Commonly used in outdoor activities, repellents can be found in various forms, including sprays, lotions, and candles. They work by masking scents or emitting odors that are unpleasant to pests, making the area less attractive to them. Insect repellents often contain active ingredients like DEET or picaridin, which are effective against mosquitoes and ticks. These products are essential for preventing bites and reducing the risk of diseases, such as West Nile virus or Lyme disease, which can be transmitted by these pests.